PAPER 073: TOTAL HIP REPLACEMENT OUTCOMES AND THE INFLUENCE OF MORBID OBESITY

Abstract

Purpose: The increasing trend of morbidly obese patients (BMI 40+) requiring joint replacement is becoming a growing concern in Total Hip Replacement (THR) surgery. The purpose of this study was to investigate the influence that BMI may have on implant longevity and clinical outcome using prospectively collected patient data.

Method: A consecutive cohort of 2864 THR’s in 2488 patients with osteoarthritis and a minimum 2 years follow-up were evaluated. Patients were divided into appropriate BMI categories; Normal and Underweight (BMI< 25, n=650), Overweight (BMI 25–29.9, n=1069), Obese (BMI 30–39.9, n=981), and Morbidly Obese (BMI 40+, n=164). Pre-operative, latest, and change in clinical outcome scores (HSS, SF12, WOMAC) were analyzed using ANOVA and Kaplan-Meier (K-M) survivorship was determined. Categorical variables such as gender and survival status were analyzed using chi-squared.

Results: Morbidly Obese patients requiring THR’s were significantly younger than all other BMI groups by 5.4±0.83 years (p< 0.0001). Gender was also significant to BMI grouping with more females being Morbidly Obese and Normal or Underweight (p< 0.0001). All pre-operative and latest HHS and WOMAC domain scores were lower for the Morbidly Obese, significantly in all preoperative score domains and latest HHS Function (p< 0.05). The change in clinical scores from pre-operative to latest was greatest in all domains for the Morbidly Obese group. K-M cumulative survival with implant revision as the endpoint at 10 years was not different between the BMI groups. Revision rates for infection for the Morbidly Obese, Obese, Overweight, and Normal were 1.3%, 0.65%, 0.3% and 0.69% respectively. Overall Revision rates for the Morbidly Obese, Obese, Overweight, and Normal were 6.7%, 5.4%, 6.9% and 5.7% respectively and were not found to be significant (p=0.496).

Conclusion: The Morbidly Obese cohort undergoing THR had significantly lower preoperative and lower postoperative clinical outcome scores than all other BMI groups but demonstrated the most significant improvement. No difference was found in the K-M survivorship although revisions and revisions for infection were not equal between the groups